An image projection system such as a projection television or a video projector generates an image by using a specially manufactured image display medium such as a small cathode-ray tube (CRT) or a liquid crystal display, magnifies the image by using a projection lens, and projects the magnified image on a large screen.
An image projection system includes a red monochrome CRT, a green monochrome CRT, a blue monochrome CRT, a first projection lens, a second projection lens, a third projection lens and a screen. The red, the green and the blue monochrome CRTs respectively serve as image sources, respectively correspond to the first, the second and the third projection lenses, and respectively generate a red image, a green image and a blue image. The first projection lens enlarges and projects the red image; the second projection lens enlarges and projects the green image; and the third projection lens enlarges and projects the blue image. The first, the second and the third projection lenses superpose the red, the green and the blue images onto the screen to cause the screen to receive a projected light.
The screen distributes the projected light properly so that the distribution of the projected light can be perceived as an image from various angles. The screen generally includes a Fresnel lens sheet and a lenticular lens array sheet. The Fresnel lens sheet causes the projected light to converge and converts the projected light into a substantially parallel light, wherein the projected light enters the screen divergently from the center to the periphery of the screen. The lenticular lens array sheet diffuses the projected light converted into the substantially parallel light so that the projected light can be perceived as an image from various angles.
The lenticular lens array sheet for diffusing the projected light instead of a simple diffusion sheet can implement an anisotropic diffusion function and a color-shift correction function.
The anisotropic diffusion function can effectively distribute a limited light and increase the luminance in the effective observation region. The anisotropic diffusion function is generally provided by adding a diffusion material inside the lenticular lens array sheet so as to provide a relatively wide angle of view in the horizontal direction and provide a relatively narrow angle of view in the vertical direction. The lenticular lens array sheet includes an incident side and an emergent side. For the color shift correction function, two lenticular lens arrays are respectively provided on the incident side and the emergent side.
The image projection system can have a further application and variation.